This invention is concerned with a machine for lasting side portions of shoe uppers comprising a shoe support for supporting, bottom up, a shoe on a last with an insole on the last bottom, and two side lasting assemblies, arranged one at each side of the shoe support, for operating progressively along opposite side portions of a shoe supported by the shoe support in a direction from the heel end to the toe end, wherein each side lasting assembly comprises a lasting roller having a helical rib arrangement which, as the roller is caused to rotate in engagement with a lasting marginal portion of the upper of such shoe, effects an inwiping action on said portion and presses it against a corresponding marginal portion of the insole of such shoe.
One such machine is described e.g. in GB-A 1 493 937.
In lasting side portions of shoe uppers using a lasting roller of the aforementioned type desirably the surface of the lasting roller should lie firmly against the flat surface of the shoe bottom or, where the surface of the shoe bottom is curved, the surface of the roller should lie tangentially thereto. In order to achieve such an arrangement six separate movements can be identified, namely:
movement lengthwise of the shoe (X-axis movement); PA1 movement widthwise of the shoe (Y-axis movement); PA1 movement heightwise of the shoe (Z-axis movement); PA1 movement about an axis extending parallel to the Z-axis PA1 movement (swing movement); PA1 movement about an axis extending parallel to the Y-axis PA1 movement (tilt movement); and PA1 rotation of the roller.
In the machine described in GB-A 1 493 937 clearly X-axis movement, Z-axis movement and also tilt movement can be effected, but the rollers are arranged with their axes of rotation parallel with each other and with the direction of the Y-axis. Moreover, in said machine, because of the width of the rollers in relation to the width of the lasting marginal portions of shoe uppers to be operated upon, no requirement for Y-axis movement was perceived.
While said machine carried out satisfactory lasting operations in a wide range of cases, nevertheless in certain cases, notably where the shoe upper patterns were poorly cut in relation to the shape of the last, problems occurred in particular at the "outside" of the shoe in the ball region thereof, where the region to be lasted meets the previously toe-lasted portion of the shoe upper, in that a so-called "loop" was frequently found to arise.
One of the problems in determining optimum conditions for operating upon shoe bottoms arises in that different requirements can be identified for the "inside" and "outside" of a shoe bottom. For example it has been established that in order to avoid the formation of a loop at the ball region on the outside of the shoe, as discussed above, preferably the axis of the lasting roller should be inclined to a longitudinal centre line of the shoe support, with the free end of the roller directed towards the heel end of the shoe. For operating on the inside of the shoe, on the other hand, ideally inclining the axis of the roller towards the longitudinal centre line of the shoe support, with the free end of the roller directed towards the toe end of the shoe would appear to give beneficial results, in terms of tightly lasting the upper material to the shape of the last in especially the inside waist region. Moreover, it has further been found that it is beneficial when operating on the outside of the shoe for the direction of rotation of the roller to be such that the surface in engagement with the shoe is moving toewardly, while in the case of the inside of the shoe, as described above, preferably the surface of the roller in engagement with the shoe should be moving heelwardly.
One solution would of course be to provide two rolls at each side of the shoe bottom and utilise one or other, according to whether the shoe being operated upon is a left or a right. Not only is such a solution expensive, however, but also there is a question of space for accommodating two rollers at each side, especially in a situation where such rollers are angled significantly from one another.